One of the performance measures of an RF (radio frequency) circuit is noise figure. Since noise figure relates to signal-reception sensitivity, a product equipped with an RF circuit is subjected to noise figure evaluation at the time of shipment in order to ensure that the noise figure is within the specification range.
In the case of an automotive radar utilizing a 77-GHz band, for example, the noise of an RF circuit is measured in the high-frequency region around 77 GHz. Such measurement involves the use of an expensive evaluation apparatus such as a spectrum analyzer for the purpose of evaluating noise in high-frequency range, which leads to an increase in the manufacturing cost. In order to reduce cost, it is desirable to provide a mechanism for measuring noise levels inside an RF chip without resort to the use of an expensive evaluation apparatus.
Noise power levels are extremely low in the case of thermal noise at room temperature. Measuring noise power thus involves the use of a high-gain and low-noise amplifier that can amplify minute noise signals by a large factor. It is difficult, however, to provide such a high-quality amplifier embedded in a chip by using the inexpensive Si-CMOS process. Conventionally, an amplifier module utilizing a compound semiconductor is provided as an embedded element in an evaluation device to perform noise evaluation.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2004-318711    [Patent Document 2] Japanese Laid-open Patent Publication No. 2001-154754    [Patent Document 3] Japanese Laid-open Patent Publication No. H10-240370